U.S. patent application number 16/820119 was filed with the patent office on 2021-03-11 for image forming apparatus.
This patent application is currently assigned to FUJI XEROX CO., LTD.. The applicant listed for this patent is FUJI XEROX CO., LTD.. Invention is credited to Osamu Handa.
Application Number | 20210072672 16/820119 |
Document ID | / |
Family ID | 1000004720446 |
Filed Date | 2021-03-11 |
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United States Patent
Application |
20210072672 |
Kind Code |
A1 |
Handa; Osamu |
March 11, 2021 |
IMAGE FORMING APPARATUS
Abstract
An image forming apparatus includes a revolving member, a
transfer member, a guide member, and a controller. The revolving
member revolves and retains a toner image on a peripheral surface
thereof. The transfer member nips a transported recording medium
and the revolving member at a nipping section and transfers the
toner image retained by the revolving member onto the recording
medium by receiving a voltage. The guide member is connected to
ground, guides the recording medium to the nipping section, and is
in contact with the recording medium nipped at the nipping section.
The controller performs constant current control to transfer the
toner image onto the recording medium if a print resistance is
lower than or equal to a system resistance. The print resistance
corresponds to when the voltage is applied to the transfer member
in a state where the recording medium is nipped at the nipping
section. The system resistance corresponds to when the voltage is
applied to the transfer member in a state where the recording
medium is not nipped at the nipping section.
Inventors: |
Handa; Osamu; (Kanagawa,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
FUJI XEROX CO., LTD. |
Tokyo |
|
JP |
|
|
Assignee: |
FUJI XEROX CO., LTD.
Tokyo
JP
|
Family ID: |
1000004720446 |
Appl. No.: |
16/820119 |
Filed: |
March 16, 2020 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G03G 15/165 20130101;
G03G 15/1645 20130101; G03G 15/1675 20130101 |
International
Class: |
G03G 15/16 20060101
G03G015/16 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 10, 2019 |
JP |
2019-164714 |
Claims
1. An image forming apparatus comprising: a revolving member that
revolves and that retains a toner image on a peripheral surface
thereof; a transfer member that nips a transported recording medium
and the revolving member at a nipping section and that transfers
the toner image retained by the revolving member onto the recording
medium by receiving a voltage; a guide member that is connected to
ground, guides the recording medium to the nipping section, and is
in contact with the recording medium nipped at the nipping section;
and a controller that performs constant current control to transfer
the toner image onto the recording medium if a print resistance is
lower than or equal to a system resistance, the print resistance
corresponding to when the voltage is applied to the transfer member
in a state where the recording medium is nipped at the nipping
section, the system resistance corresponding to when the voltage is
applied to the transfer member in a state where the recording
medium is not nipped at the nipping section.
2. The image forming apparatus according to claim 1, wherein the
controller performs constant voltage control to transfer the toner
image onto the recording medium if the print resistance is higher
than the system resistance.
3. The image forming apparatus according to claim 1, wherein the
controller calculates the print resistance in accordance with the
voltage applied to the transfer member in the state where the
recording medium is nipped at the nipping section and an electric
current flowing when the voltage is applied.
4. The image forming apparatus according to claim 2, wherein the
controller calculates the print resistance in accordance with the
voltage applied to the transfer member in the state where the
recording medium is nipped at the nipping section and an electric
current flowing when the voltage is applied.
5. The image forming apparatus according to claim 1, further
comprising: a detection member that detects image densities of a
plurality of detection images as toner images transferred onto the
recording medium, wherein the controller causes the plurality of
detection images to be transferred onto the recording medium while
varying the voltage applied to the transfer member to a plurality
of values when the detection images are transferred onto the
recording medium, selects one of the detection images from the
image densities of the plurality of detection images detected by
the detection member, and calculates the print resistance in
accordance with a voltage when the selected detection image is
transferred and an electric current flowing when the voltage is
applied.
6. The image forming apparatus according to claim 2, further
comprising: a detection member that detects image densities of a
plurality of detection images as toner images transferred onto the
recording medium, wherein the controller causes the plurality of
detection images to be transferred onto the recording medium while
varying the voltage applied to the transfer member to a plurality
of values when the detection images are transferred onto the
recording medium, selects one of the detection images from the
image densities of the plurality of detection images detected by
the detection member, and calculates the print resistance in
accordance with a voltage when the selected detection image is
transferred and an electric current flowing when the voltage is
applied.
7. The image forming apparatus according to claim 5, wherein the
controller causes the plurality of detection images to be
transferred onto a single recording medium.
8. The image forming apparatus according to claim 6, wherein the
controller causes the plurality of detection images to be
transferred onto a single recording medium.
9. The image forming apparatus according to claim 1, further
comprising: an input unit to which information about one of a
plurality of confirmation images as toner images transferred onto
the recording medium is input, the one confirmation image being
selected by a user from the plurality of confirmation images,
wherein the controller causes the plurality of confirmation images
to be transferred onto the recording medium while varying the
voltage applied to the transfer member to a plurality of values
when the confirmation images are transferred onto the recording
medium, and calculates the print resistance in accordance with a
voltage when the input confirmation image is transferred and an
electric current flowing when the voltage is applied, based on the
information about the confirmation image input to the input
unit.
10. The image forming apparatus according to claim 2, further
comprising: an input unit to which information about one of a
plurality of confirmation images as toner images transferred onto
the recording medium is input, the one confirmation image being
selected by a user from the plurality of confirmation images,
wherein the controller causes the plurality of confirmation images
to be transferred onto the recording medium while varying the
voltage applied to the transfer member to a plurality of values
when the confirmation images are transferred onto the recording
medium, and calculates the print resistance in accordance with a
voltage when the input confirmation image is transferred and an
electric current flowing when the voltage is applied, based on the
information about the confirmation image input to the input
unit.
11. The image forming apparatus according to claim 9, wherein the
controller causes the information about the confirmation image
applied to the transfer member to be displayed on the recording
medium when the confirmation image is to be transferred onto the
recording medium.
12. The image forming apparatus according to claim 10, wherein the
controller causes the information about the confirmation image
applied to the transfer member to be displayed on the recording
medium when the confirmation image is to be transferred onto the
recording medium.
13. A image forming apparatus comprising: revolving means for
retaining a toner image on a peripheral surface thereof;
transferring means for nipping a transported recording medium and
the revolving means at a nipping section and for transferring the
toner image retained by the revolving means onto the recording
medium by receiving a voltage; guiding means connected to ground,
the guiding means guiding the recording medium to the nipping
section and being in contact with the recording medium nipped at
the nipping section; and control means for performing constant
current control to transfer the toner image onto the recording
medium if a print resistance is lower than or equal to a system
resistance, the print resistance corresponding to when the voltage
is applied to the transferring means in a state where the recording
medium is nipped at the nipping section, the system resistance
corresponding to when the voltage is applied to the transferring
means in a state where the recording medium is not nipped at the
nipping section.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is based on and claims priority under 35
USC 119 from Japanese Patent Application No. 2019-164714 filed Sep.
10, 2019.
BACKGROUND
(i) Technical Field
[0002] The present disclosure relates to image forming
apparatuses.
(ii) Related Art
[0003] An image forming apparatus disclosed in Japanese Unexamined
Patent Application Publication No. 2003-302846 performs
programmable transfer voltage control (PTVC) to set a transfer
voltage and applies a constant voltage. In this system, when a
voltage to be applied is to be set by detecting a transfer current
at the leading edge of a transfer member and comparing the detected
transfer current with a threshold value, this threshold value is
changed by referring to sheet-feed-port information.
SUMMARY
[0004] In the image forming apparatus in the related art, the
transfer member having received a voltage nips a revolving member,
which retains a toner image thereon, and a recording medium, and
transfers the toner image on the revolving member onto the
recording medium.
[0005] In such an image forming apparatus, when the toner image
retained by the revolving member is to be transferred onto the
recording medium, the toner image is transferred onto the recording
medium in accordance with constant voltage control. However, if the
recording medium used is a low-resistance medium having a low
surface resistance, a transfer defect may occur with the constant
voltage control.
[0006] Aspects of non-limiting embodiments of the present
disclosure relate to suppressing the occurrence of a transfer
defect of a toner image onto a low-resistance medium, as compared
with a case where a toner image is transferred onto a recording
medium consistently in accordance with constant voltage
control.
[0007] Aspects of certain non-limiting embodiments of the present
disclosure address the above advantages and/or other advantages not
described above. However, aspects of the non-limiting embodiments
are not required to address the advantages described above, and
aspects of the non-limiting embodiments of the present disclosure
may not address advantages described above.
[0008] According to an aspect of the present disclosure, there is
provided an image forming apparatus including a revolving member, a
transfer member, a guide member, and a controller. The revolving
member revolves and retains a toner image on a peripheral surface
thereof. The transfer member nips a transported recording medium
and the revolving member at a nipping section and transfers the
toner image retained by the revolving member onto the recording
medium by receiving a voltage. The guide member is connected to
ground, guides the recording medium to the nipping section, and is
in contact with the recording medium nipped at the nipping section.
The controller performs constant current control to transfer the
toner image onto the recording medium if a print resistance is
lower than or equal to a system resistance. The print resistance
corresponds to when the voltage is applied to the transfer member
in a state where the recording medium is nipped at the nipping
section. The system resistance corresponds to when the voltage is
applied to the transfer member in a state where the recording
medium is not nipped at the nipping section.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] Exemplary embodiments of the present disclosure will be
described in detail based on the following figures, wherein:
[0010] FIG. 1 is a side view illustrating a transfer member and
other components included in an image forming apparatus according
to a first exemplary embodiment of the present disclosure;
[0011] FIG. 2 is a side view illustrating the transfer member and
other components included in the image forming apparatus according
to the first exemplary embodiment of the present disclosure;
[0012] FIG. 3 is a side view illustrating the transfer member and
other components included in the image forming apparatus according
to the first exemplary embodiment of the present disclosure;
[0013] FIG. 4 is a front view illustrating the transfer member and
other components included in the image forming apparatus according
to the first exemplary embodiment of the present disclosure;
[0014] FIG. 5 is a front view illustrating the transfer member and
other components included in the image forming apparatus according
to the first exemplary embodiment of the present disclosure;
[0015] FIG. 6 illustrates the configuration of a part of a user
interface of the image forming apparatus according to the first
exemplary embodiment of the present disclosure;
[0016] FIG. 7 is a flowchart illustrating the flow of control of
each component by a controller of the image forming apparatus
according to the first exemplary embodiment of the present
disclosure;
[0017] FIG. 8 is a block diagram illustrating a control system of
the controller of the image forming apparatus according to the
first exemplary embodiment of the present disclosure;
[0018] FIG. 9 is a graph illustrating a voltage used for
transferring a toner image onto a sheet member for each sheet type,
in the image forming apparatus according to the first exemplary
embodiment of the present disclosure;
[0019] FIG. 10 is a configuration diagram illustrating a
toner-image forming unit of the image forming apparatus according
to the first exemplary embodiment of the present disclosure;
[0020] FIG. 11 is a configuration diagram illustrating an image
forming unit of the image forming apparatus according to the first
exemplary embodiment of the present disclosure;
[0021] FIG. 12 is a configuration diagram schematically
illustrating the image forming apparatus according to the first
exemplary embodiment of the present disclosure;
[0022] FIG. 13 is a block diagram illustrating a control system of
a controller of an image forming apparatus according to a
comparative example relative to the first exemplary embodiment of
the present disclosure;
[0023] FIG. 14 is a flowchart illustrating the flow of control of
each component by a controller of an image forming apparatus
according to a second exemplary embodiment of the present
disclosure;
[0024] FIG. 15 is a block diagram illustrating a control system of
the controller of the image forming apparatus according to the
second exemplary embodiment of the present disclosure;
[0025] FIG. 16 illustrates detection images output by the image
forming apparatus according to the second exemplary embodiment of
the present disclosure;
[0026] FIG. 17 is a flowchart illustrating the flow of control of
each component by a controller of an image forming apparatus
according to a third exemplary embodiment of the present
disclosure;
[0027] FIG. 18 is a block diagram illustrating a control system of
the controller of the image forming apparatus according to the
third exemplary embodiment of the present disclosure;
[0028] FIG. 19 illustrates the configuration of a part of a user
interface of the image forming apparatus according to the third
exemplary embodiment of the present disclosure;
[0029] and
[0030] FIG. 20 illustrates confirmation images output by the image
forming apparatus according to the third exemplary embodiment of
the present disclosure.
DETAILED DESCRIPTION
First Exemplary Embodiment
[0031] An example of an image forming apparatus according to a
first exemplary embodiment of the present disclosure will be
described with reference to FIGS. 1 to 12. In each of the drawings,
an arrow H indicates an up-down direction as a vertical direction
of the apparatus, an arrow W indicates a width direction as a
horizontal direction of the apparatus, and an arrow D indicates a
depth direction as another horizontal direction of the
apparatus.
Overall Configuration of Image Forming Apparatus
[0032] As shown in FIG. 12, an image forming apparatus 10 includes
an image forming unit 12 that forms an image by electrophotography,
and also includes a transport device 18 having multiple transport
rollers (not given reference signs) that transport a sheet member P
(as an example of a recording medium) along a transport path 16 of
the sheet member P.
[0033] Moreover, the image forming apparatus 10 includes a cooler
20 that cools the sheet member P having an image formed thereon, a
corrector 22 that corrects bending of the sheet member P, an image
inspector 24 that inspects the image formed on the sheet member P,
and a controller 36 that controls each component. The image
inspector 24, the controller 36, and the transport device 18 will
be described in detail later.
[0034] Furthermore, for forming images on opposite faces of the
sheet member P, the image forming apparatus 10 includes an
inversion path 26 used for inverting the sheet member P having an
image formed on the front face thereof and transporting the sheet
member P toward the image forming unit 12 again.
[0035] In the image forming apparatus 10 having this configuration,
an image (i.e., a toner image) formed by the image forming unit 12
is formed on the front face of the sheet member P transported along
the transport path 16. Moreover, the sheet member P having the
image formed thereon travels through the cooler 20, the corrector
22, and the image inspector 24 in this order so as to be output
from the apparatus.
[0036] If an image is to be formed on the rear face of the sheet
member P, the sheet member P having the image formed on the front
face thereof is transported along the inversion path 26, so that an
image is formed again on the rear face of the sheet member P by the
image forming unit 12.
Image Forming Unit 12
[0037] The image forming unit 12 includes multiple toner-image
forming units 30 that individually form toner images of respective
colors, and also includes a transfer unit 14 that is provided with
a transfer belt 50 for retaining the toner images thereon and that
transfers the toner images onto the sheet member P. Furthermore,
the image forming unit 12 includes a fixing device 34 that fixes
the toner images transferred on the sheet member P by the transfer
unit 14 onto the sheet member P. The transfer unit 14 will be
described in detail later.
[0038] The multiple toner-image forming units 30 form toner images
of respective colors. In this exemplary embodiment, there are four
toner-image forming units 30 provided for yellow (Y), magenta (M),
cyan (C), and black (K) colors. In FIG. 12, Y, M, C, and K denote
the respective colors. In the following description, if the yellow
(Y), magenta (M), cyan (C), and black (K) colors are not to be
distinguished from one another, Y, M, C, and K added to the
reference signs will be omitted.
[0039] The toner-image forming units 30 for the respective colors
basically have identical configurations except for the toners used,
and each include a rotating cylindrical image bearing member 40 and
a charger 42 that electrostatically charges the image bearing
member 40, as shown in FIG. 10. Furthermore, each toner-image
forming unit 30 includes an exposure device 44 that forms an
electrostatic latent image by radiating exposure light onto the
electrostatically-charged image bearing member 40, and also
includes a developing device 46 that develops the electrostatic
latent image into a toner image by using a developer G that
contains a toner. The developer G used in this exemplary embodiment
is a two-component developer containing a toner and a carrier.
[0040] The image bearing members 40 for the respective colors are
connected to ground and are in contact with the transfer belt 50
(to be described in detail later) that moves in a revolving
fashion. As shown in FIG. 12, the toner-image forming units 30 for
the yellow (Y), magenta (M), cyan (C), and black (K) colors are
arranged in the horizontal direction in this order from upstream in
the revolving direction (indicated by an arrow A) of the transfer
belt 50.
[0041] As shown in FIG. 12, the fixing device 34 includes a heated
fixing belt 60 wrapped around multiple rollers (without reference
signs) and a pressing roller 62 that presses the sheet member P
toward the fixing belt 60.
[0042] In this configuration, the sheet member P having the toner
images transferred thereon is nipped and transported by the
revolving fixing belt 60 and the pressing roller 62, so that the
toner images are fixed onto the sheet member P. Configuration of
Relevant Components
[0043] Next, the transfer unit 14, the image inspector 24, the
transport device 18, and the controller 36 will be described.
Transfer Unit 14
[0044] As shown in FIG. 11, the transfer unit 14 includes the
transfer belt 50, multiple rollers 32 around which the transfer
belt 50 is wrapped, and first-transfer rollers 52 that transfer the
toner images on the image bearing members 40 onto the transfer belt
50. Furthermore, the transfer unit 14 includes a second-transfer
roller 54 that transfers the toner images transferred on the
transfer belt 50 onto the sheet member P, and also includes a
high-voltage power supply 68 (see FIG. 1). The transfer belt 50 is
an example of a revolving member.
Transfer Belt 50
[0045] As shown in FIG. 11, the transfer belt 50 is endless and is
wrapped around the multiple rollers 32. As viewed from the depth
direction of the apparatus, the transfer belt 50 is positioned to
have an inverted obtuse triangular shape that is long in the width
direction of the apparatus. In this exemplary embodiment, the
transfer belt 50 is composed of, for example, a material with
carbon dispersed in polyimide. Moreover, the transfer belt 50 has a
volume resistivity of 12.5 log .OMEGA.cm.
Rollers 32
[0046] As shown in FIG. 11, the multiple rollers 32 are provided.
Among the multiple rollers 32, a roller 32d disposed at one side
(i.e., the right side) in the width direction of the apparatus
receives a rotational force from a motor (not shown) so as to cause
the transfer belt 50 to revolve in the direction of the arrow A
(i.e., counterclockwise direction).
[0047] Furthermore, the multiple rollers 32 include a roller 32b
over which the obtuse lower apex of the transfer belt 50 positioned
to have the obtuse triangular shape is looped. The roller 32b is
disposed opposite the second-transfer roller 54, to be described
later, with the transfer belt 50 interposed therebetween, and
receives a voltage. In this exemplary embodiment, the roller 32b
is, for example, an elastic roller having an outer diameter of 28
mm. Furthermore, the roller 32b has a surface resistance of 7.3 log
.OMEGA./sq. The roller 32b has a surface hardness, that is, an
Asker C hardness, of 53 degrees.
[0048] Among the multiple rollers 32, a roller 32t disposed next to
the roller 32b at the upstream side thereof in the revolving
direction of the transfer belt 50 (referred to as "belt revolving
direction" hereinafter) applies tension to the transfer belt
50.
First-Transfer Rollers 52
[0049] As shown in FIG. 11, the first-transfer rollers 52 are
disposed opposite the image bearing members 40 of the respective
colors with the transfer belt 50 interposed therebetween.
[0050] In this configuration, a transfer current flows to each
first-transfer roller 52 so that a transfer electric field is
generated between the first-transfer roller 52 and the image
bearing member 40. This transfer electric field causes the toner
image on each image bearing member 40 to be transferred onto the
transfer belt 50.
Second-Transfer Roller 54
[0051] As shown in FIG. 1, the second-transfer roller 54 is
connected to ground and nips the transfer belt 50 together with the
roller 32b. In this exemplary embodiment, the second-transfer
roller 54 is, for example, an elastic roller having an outer
diameter of 28 mm. Furthermore, the second-transfer roller 54 has a
resistance of 6.3 log .OMEGA..
High-Voltage Power Supply 68
[0052] The high-voltage power supply 68 has a function of applying
a direct-current voltage to the roller 32b so as to apply an
electric current thereto. As shown in FIG. 1, the high-voltage
power supply 68 has an ammeter 68a that may monitor an electric
current flowing through the roller 32b, and also has a voltmeter
68b that may monitor a voltage applied to the roller 32b.
[0053] In this configuration, the sheet member P transported while
being nipped at a second-transfer section NT between the transfer
belt 50 and the second-transfer roller 54 is pressed toward the
transfer belt 50. Then, a voltage is applied to the roller 32b, so
that an electric current flows between the roller 32b and the
second-transfer roller 54, whereby a transfer electric field is
generated. This transfer electric field causes a toner image
retained by the transfer belt 50 to be transferred onto the
transported sheet member P at the second-transfer section NT. The
second-transfer section NT is an example of a nipping section.
[0054] Accordingly, the second-transfer roller 54 and the roller
32b constitute a transfer member 56 that nips the transported sheet
member P and the transfer belt 50 and that transfers the toner
image retained by the transfer belt 50 onto the sheet member P.
Image Inspector 24
[0055] As shown in FIG. 12, the image inspector 24 is disposed
downstream of the fixing device 34 in the transport direction of
the sheet member P (referred to as "sheet transport direction"
hereinafter). The image inspector 24 radiates light toward the
sheet member P having the toner image formed thereon, receives the
reflected light, and detects the density of the toner image (toner
image density) based on the intensity of the received light. The
image inspector 24 is an example of a detection member.
Transport Device 18
[0056] As shown in FIG. 12, the transport device 18 includes
containers 70 containing sheet members P therein, multiple
transport rollers (not given reference signs) that transport each
of the sheet members P contained in the containers 70 along the
transport path 16, and a guide member 64 that guides each
transported sheet member P toward the second-transfer section
NT.
[0057] As shown in FIG. 1, the guide member 64 is connected to
ground and is disposed in contact with the sheet member P whose
leading edge is nipped at the second-transfer section NT at the
upstream side of the second-transfer section NT in the sheet
transport direction (see FIG. 2). In detail, the sheet member P
being transported curves so that the guide member 64 comes into
contact with the sheet member P. The guide member 64 is composed of
a conductive material and includes a tabular guide plate 64a that
covers the sheet member P from above and a tabular guide plate 64b
that supports the sheet member P from below. Accordingly, the guide
member 64 functions as a charge remover that removes an electric
charge from the sheet member P. The conductive material has an
electrical conductivity of 10.sup.6 S/m or higher.
Miscellaneous Components
[0058] As shown in FIG. 6, a user interface 72 of the image forming
apparatus 10 is provided with an input unit 74 to which information
about the sheet members P contained in the containers 70 (see FIG.
12) is input.
[0059] The input unit 74 is provided with a sheet-type input unit
74a to which the sheet type of sheet members P contained in each
container 70 is input and a sample output unit 74b that outputs a
toner image of a sample pattern to a sheet member P contained in
one of the containers 70. When the user touches the sample output
unit 74b, the toner image of the sample pattern is formed on the
sheet member P contained in the container 70, and control of the
high-voltage power supply 68 by the controller 36 is set. This will
be described in detail later.
Controller 36
[0060] As shown in FIG. 8, the controller 36 controls the
high-voltage power supply 68 based on information input to the
input unit 74 by the user. The control of the high-voltage power
supply 68 by the controller 36 will be described later together
with the operation.
Operation of Relevant Components
[0061] Next, the operation of the relevant components will be
described while being compared with an image forming apparatus 510
according to a comparative example. With regard to the
configuration and the operation of the image forming apparatus 510
according to the comparative example, features different from those
of the image forming apparatus 10 will be described.
Configuration of Image Forming Apparatus 510
[0062] As shown in FIG. 13, the image forming apparatus 510
includes a controller 536. The controller 536 controls the
high-voltage power supply 68.
Operation of Image Forming Apparatuses 10 and 510
[0063] In a state where the power of the image forming apparatus 10
shown in FIG. 12 is turned off, all components are stopped. When
the user turns on the power of the image forming apparatus 10, the
controller 36 or 536 shown in FIG. 1 controls the high-voltage
power supply 68 so as to cause an electric current of a
predetermined current value to flow to the roller 32b. Moreover,
the controller 36 or 536 acquires a voltage from the voltmeter 68b
when the electric current flows through the roller 32b, and
calculates a system resistance from the electric current flowing
through the roller 32b and the voltage acquired from the voltmeter
68b.
[0064] A "system resistance" is a combined resistance of the roller
32b, the transfer belt 50, and the second-transfer roller 54 when
an electric current used for transferring a toner image onto a
sheet member P flows through the roller 32b in a state where the
sheet member P is not nipped at the second-transfer section NT.
Controller 536 in Image Forming Apparatus 510
[0065] In a case where a toner image is to be transferred onto a
sheet member P, the controller 536 included in the image forming
apparatus 510 according to the comparative example applies a
voltage of a predetermined value to the roller 32b based on the
aforementioned system resistance and sheet-type information input
to the sheet-type input unit 74a by the user. Then, the controller
536 consistently performs constant voltage control to transfer the
toner image onto the sheet member P.
[0066] In detail, the controller 536 sets a voltage to be applied
to the roller 32b by using a print resistance in a state where
plain paper as a sheet member P is nipped at the second-transfer
section NT. The print resistance is set in accordance with
sheet-type information preliminarily stored in the image forming
apparatus 510 and sheet-type information input to the sheet-type
input unit 74a.
[0067] "Constant voltage control" involves performing control to
match an output voltage value with a target voltage value. "Plain
paper" is a recording medium normally used in image forming
apparatuses and has a surface resistivity (JIS K 6911) greater than
10.sup.6 .OMEGA./sq. A "print resistance" is a combined resistance
of the roller 32b, the transfer belt 50, the second-transfer roller
54, the sheet member P, and the guide member 64 when an electric
current used for transferring a toner image onto a sheet member P
flows to the roller 32b in a state where the sheet member P is
nipped at the second-transfer section NT.
[0068] FIG. 9 illustrates a graph having an ordinate axis
indicating a voltage applied to the roller 32b when an electric
current used for transferring a toner image onto a sheet member P
flows to the roller 32b and an abscissa axis indicating a system
resistance. A solid line L01 indicates a voltage when the sheet
member P is not nipped at the second-transfer section NT, and a
dashed line L02 indicates a voltage when plain paper as the sheet
member P is nipped at the second-transfer section NT.
[0069] As shown in FIG. 2, when a voltage is applied to the roller
32b in a state where plain paper as the sheet member P is nipped at
the second-transfer section NT, the electric current flows toward
the second-transfer roller 54 from the roller 32b (see an arrow E01
in FIG. 2). Thus, the print resistance when the plain paper as the
sheet member P is nipped at the second-transfer section NT becomes
higher than the system resistance.
[0070] It is clear from the graph shown in FIG. 9 that, when a
toner image is to be transferred onto the plain paper as the sheet
member P (see the dashed line L02), a high voltage has to be
applied to the roller 32b, as compared with a case where the sheet
member P is not nipped at the second- transfer section NT (see the
solid line L01).
[0071] For example, in a case where the system resistance is R01, a
voltage to be applied to the roller 32b is V01 when an electric
current used for transferring the toner image onto the sheet member
P flows to the roller 32b in a state where the sheet member P is
not nipped at the second-transfer section NT. Furthermore, in a
case where the system resistance is R01, a voltage to be applied to
the roller 32b is V02 when an electric current used for
transferring the toner image onto the sheet member P flows to the
roller 32b in a state where plain paper as the sheet member P is
nipped at the second-transfer section NT. The voltage V02 is higher
than the voltage V01.
[0072] Accordingly, in the image forming apparatus 510, the roller
32b receives a voltage higher than the voltage applied to the
roller 32b when an electric current used for transferring the toner
image onto the sheet member P flows to the roller 32b in a state
where the sheet member P is not nipped at the second-transfer
section NT.
[0073] The electric current flows between the roller 32b and the
second-transfer roller 54 in accordance with the applied voltage,
so that a transfer electric field is generated. This transfer
electric field causes the toner image retained by the transfer belt
50 to be transferred onto the sheet member P. Accordingly, in the
image forming apparatus 510, a toner image is transferred onto a
sheet member P consistently in accordance with constant voltage
control.
[0074] The reason for performing the constant voltage control will
be described here. FIG. 5 illustrates an electric current flowing
from the roller 32b toward the second-transfer roller 54 when a
voltage is applied to the roller 32b in a state where plain paper
as a sheet member P is nipped at the second-transfer section NT.
However, the electric current value varies between an electric
current (see an arrow E11 in FIG. 5) flowing to an area where the
sheet member P is nipped and an electric current (see arrows E12 in
FIG. 5) flowing to areas where the sheet member P is not nipped.
Therefore, it is difficult to control the electric current value of
the electric current E11 flowing to the area where the sheet member
P is nipped. The controller 536 included in the image forming
apparatus 510 transfers the toner image onto the sheet member P
consistently in accordance with constant voltage control.
[0075] The following description relates to a case where a
low-resistance medium is used as a sheet member P. A
"low-resistance medium" is a recording medium that has a surface
resistivity lower than that of plain paper and that has a surface
resistivity (JIS K 6911) lower than or equal to 10.sup.6
.OMEGA./sq, such as metallized paper having metal deposited on its
surface or black paper given black color by a pigment.
[0076] As shown in FIG. 3, when a voltage is applied to the roller
32b in a state where a low-resistance medium as a sheet member P is
nipped at the second-transfer section NT, because the surface
resistivity of the sheet member P is low, the electric current
flows from the roller 32b to the sheet member P and then toward the
guide member 64 composed of a conductive material (see an arrow E02
in FIG. 3).
[0077] Therefore, as shown in FIG. 4, the electric current does not
flow through areas where the sheet member P is not nipped. The
electric current flows from the roller 32b to the sheet member P
and then toward the guide member 64. Thus, in a state where the
low-resistance medium as the sheet member P is nipped at the
second-transfer section NT, the print resistance becomes equal to
or lower than the system resistance. Accordingly, the guide member
64 functions as a controller that controls the direction of the
flow of the electric current such that the electric current flows
along the sheet surface of the sheet member P.
[0078] A single-dot chain line L03 in the graph in FIG. 9 indicates
a voltage applied to the roller 32b when an electric current used
for transferring a toner image onto a sheet member P flows to the
roller 32b in a state where a low-resistance medium as a sheet
member P is nipped at the second-transfer section NT. As mentioned
above, in a state where the low-resistance medium is nipped at the
second-transfer section NT, the print resistance is equal to or
lower than the system resistance. Therefore, in a case where the
toner image is to be transferred onto the low-resistance medium
(i.e., the case of the single-dot chain line), it is clear from the
graph in FIG. 9 that a low voltage has to be applied to the roller
32b, as compared with a case where the sheet member P is not nipped
at the second-transfer section NT (see the solid line L01). The
single-dot chain line L03 shown in FIG. 9 corresponds to a
low-resistance medium with a surface resistivity of 10.sup.3
.OMEGA./sq.
[0079] For example, in a case where the system resistance is R01, a
voltage to be applied to the roller 32b is V03 when an electric
current used for transferring a toner image onto a sheet member P
flows to the roller 32b in a state where the low-resistance medium
as the sheet member P is nipped at the second-transfer section
NT.
[0080] However, in the image forming apparatus 510 according to the
comparative example, the toner image is transferred onto the sheet
member P consistently in accordance with constant voltage control.
In the image forming apparatus 510, a high voltage is consistently
applied to the roller 32b, as compared with a case where the sheet
member P is not nipped at the second-transfer section NT (see the
solid line L01).
[0081] Therefore, in the case where the low-resistance medium is
used as the sheet member P in the image forming apparatus 510, the
toner transferability decreases, possibly causing a transfer defect
to occur when the toner image is transferred onto the sheet member
P.
Controller 36 in Image Forming Apparatus 10
[0082] Next, the operation performed on the high-voltage power
supply 68 by the controller 36 included in the image forming
apparatus 10 according to this exemplary embodiment will be
described with reference to a flowchart shown in FIG. 7.
[0083] The user sets a sheet member P in one of the containers 70
and inputs sheet-type information about the set sheet member P to
the sheet-type input unit 74a of the input unit 74. Moreover, in
order to output a sample image as a black-color toner image, the
user touches the sample output unit 74b of the input unit 74. This
causes the controller 36 to revolve the transfer belt 50 and to
control the toner-image forming unit 30K and the first-transfer
roller 52K, so as to transfer the sample image onto the transfer
belt 50 in step S100 in FIG. 7. Furthermore, the controller 36
controls the high-voltage power supply 68 so as to apply a
predetermined voltage to the roller 32b. Moreover, the controller
36 controls the transport device 18 so as to transport the sheet
member P contained in the container 70 along the transport path
16.
[0084] In step S200, the controller 36 causes the sample image to
be transferred onto the sheet member P at the second-transfer
section NT, and acquires, from the ammeter 68a, the electric
current value of the electric current flowing when the sheet member
P is nipped at the second-transfer section NT. Moreover, the
controller 36 calculates a print resistance from the acquired
electric current value and the voltage value of the voltage applied
to the roller 32b.
[0085] In step S300, the controller 36 determines whether or not
the acquired print resistance is lower than or equal to the system
resistance. If the print resistance is lower than or equal to the
system resistance, it is determined that the sheet member P is a
low-resistance medium, and the process proceeds to step S400. If
the print resistance is higher than the system resistance, it is
determined that the sheet member P is plain paper, and the process
proceeds to step S410. Accordingly, the controller 36 functions as
a determining unit that determines whether the sheet member P
nipped at the second-transfer section NT is a low-resistance medium
or plain paper.
[0086] In step S400, if a toner image is to be transferred onto the
sheet member P determined as being a low-resistance medium, the
controller 36 controls the high-voltage power supply 68 such that a
predetermined electric current flows to the roller 32b.
Specifically, the controller 36 performs constant current control
to transfer the toner image onto the sheet member P. In other
words, the controller 36 controls the voltage to be applied to the
roller 32b such that the electric current becomes equal to a
predetermined electric current value. The electric current value is
an electric current value used for transferring the toner image
onto the sheet member P. In this exemplary embodiment, the electric
current value is for a low-resistance medium and is preliminarily
stored in the image forming apparatus 10. "Constant current
control" involves matching an output electric current value with a
target electric current value.
[0087] As mentioned above, since the surface resistivity of a
low-resistance medium is low, an electric current does not flow to
areas where the sheet member P is not nipped. Most of the electric
current flows from the roller 32b to the sheet member P and then
toward the guide member 64. Specifically, the transfer electric
field where the toner image is transferred onto the sheet member P
is generated by most of the flowing electric current. Therefore, in
the case of a low-resistance medium, constant current control is
possible. Accordingly, the sequential operation ends.
[0088] In contrast, when the process proceeds to step S410 as a
result of the print resistance being higher than the system
resistance, the controller 36 applies a voltage of a predetermined
value to the roller 32b based on sheet-type information input to
the sheet-type input unit 74a by the user. In detail, the
controller 36 applies a high voltage to the roller 32b, as compared
with a case where the sheet member P is not nipped at the
second-transfer section NT. The controller 36 performs constant
voltage control in this manner to transfer the toner image onto the
sheet member P. Accordingly, the sequential operation ends.
Conclusion
[0089] As described above, in the image forming apparatus 10, if
the print resistance is lower than or equal to the system
resistance, the controller 36 determines that the sheet member P is
a low-resistance medium, and performs constant current control to
transfer the toner image onto the sheet member P. In detail, the
controller 36 causes an electric current used for transferring the
toner image onto the sheet member P to flow to the roller 32b.
Therefore, the occurrence of a transfer defect of a toner image
onto a low-resistance medium may be suppressed, as compared with
the case of the image forming apparatus 510 that transfers a toner
image onto a sheet member P consistently in accordance with
constant voltage control.
[0090] Furthermore, in the image forming apparatus 10, if the print
resistance is higher than the system resistance, the controller 36
determines that the sheet member P is plain paper, and performs
constant voltage control to transfer the toner image onto the sheet
member P. Therefore, the occurrence of a transfer defect of a toner
image onto plain paper may be suppressed, as compared with a case
where a toner image is transferred onto plain paper in accordance
with constant current control.
[0091] Moreover, in the image forming apparatus 10, when the sheet
member P is nipped at the second-transfer section NT, the
controller 36 calculates the print resistance from the voltage
applied to the roller 32b and the electric current flowing when the
voltage is applied. Therefore, the print resistance may be readily
calculated, as compared with a case where the print resistance is
calculated by using the surface resistivity of the sheet member
P.
Second Exemplary Embodiment
[0092] An example of an image forming apparatus according to a
second exemplary embodiment of the present disclosure will be
described below with reference to FIGS. 14 to 16. In the second
exemplary embodiment, features different from those in the first
exemplary embodiment will be described.
[0093] As shown in FIG. 15, an image forming apparatus 210
according to the second exemplary embodiment includes a controller
236 that controls each component.
[0094] The following description relates to control of the
high-voltage power supply 68 by the controller 236.
[0095] The user sets a sheet member P in one of the containers 70
and touches the sample output unit 74b (see FIG. 6) of the input
unit 74 to output a detection image as a black-color toner image.
This causes the controller 236 to revolve the transfer belt 50 and
to control the toner-image forming unit 30K and the first-transfer
roller 52K, so as to transfer the detection image onto the transfer
belt 50 in step S1100 in FIG. 14. Furthermore, the controller 236
controls the high-voltage power supply 68 so as to apply a voltage
to the roller 32b. Moreover, the controller 236 controls the
transport device 18 so as to transport the sheet member P contained
in the container 70 along the transport path 16.
[0096] In step S1200, the controller 236 causes multiple detection
images K01 with different voltage values of voltages applied to the
roller 32b to be transferred onto a single sheet member P at the
second-transfer section NT, as shown in FIG. 16. In detail, the
controller 236 controls the high-voltage power supply 68 to vary
the voltage value of the voltage applied to the roller 32b, whereby
multiple black-color detection images K01 are formed on the single
sheet member P for the respective voltage values. Accordingly,
multiple black-color detection images K01 with different toner
image densities are formed on the single sheet member P.
[0097] In step S1300, the image inspector 24 detects the toner
image density for each of the multiple detection images K01, and
the controller 236 receives the detection result from the image
inspector 24.
[0098] In step S1400, the controller 236 selects a detection image
K01 with a toner image density closest to a target toner image
density from the multiple detection images K01. Accordingly, the
controller 236 functions as a density selector that selects a
detection image with a toner image density closest to a target
toner image density from multiple detection images.
[0099] Furthermore, the controller 236 acquires the voltage value
of the voltage applied to the roller 32b when the selected
detection image K01 is transferred. Moreover, the controller 236
acquires, from the ammeter 68a, the electric current value of the
electric current flowing when this voltage is applied to the roller
32b. Then, the controller 236 calculates a print resistance from
the acquired electric current value and the acquired voltage
value.
[0100] In step S1500, the controller 236 determines whether or not
the acquired print resistance is lower than or equal to the system
resistance. If the print resistance is lower than or equal to the
system resistance, it is determined that the sheet member P is a
low-resistance medium, and the process proceeds to step S1600. If
the print resistance is higher than the system resistance, it is
determined that the sheet member P is plain paper, and the process
proceeds to step S1610.
[0101] In step S1600, if a toner image is to be transferred onto
the sheet member P determined as being a low-resistance medium, the
controller 236 controls the high-voltage power supply 68 such that
a predetermined electric current flows to the roller 32b. The
controller 236 performs constant current control in this manner to
transfer the toner image onto the sheet member P. Accordingly, the
sequential operation ends.
[0102] In contrast, when the process proceeds to step S1610 as a
result of the print resistance being higher than the system
resistance, the controller 236 applies a voltage of a predetermined
value to the roller 32b based on sheet-type information input to
the sheet-type input unit 74a by the user. The controller 236
performs constant voltage control in this manner to transfer the
toner image onto the sheet member P. Accordingly, the sequential
operation ends.
Conclusion
[0103] As described above, in the image forming apparatus 210, the
image inspector 24 detects the toner image density for each of the
multiple detection images K01 formed by varying the voltage value,
and the controller 236 selects a detection image K01 with a toner
image density closest to a target toner image density from the
multiple detection images K01. Furthermore, the controller 236
calculates a print resistance from the voltage value and the
electric current value when the detection image K01 is transferred.
Therefore, the accuracy of the print resistance to be calculated
may be improved, so that the occurrence of a transfer defect of a
toner image onto a low-resistance medium may be suppressed, as
compared with a case where the print resistance is calculated
without varying the voltage value of the voltage applied to the
roller 32b.
[0104] Furthermore, in the image forming apparatus 210, the
multiple black-color detection images K01 are formed on a single
sheet member P. Accordingly, the time taken for calculating the
print resistance may be shortened, as compared with a case where
multiple detection images are formed on respective sheet members
P.
Third Exemplary Embodiment
[0105] An example of an image forming apparatus according to a
third exemplary embodiment of the present disclosure will be
described below with reference to FIGS. 17 to 20. In the third
exemplary embodiment, features different from those in the first
exemplary embodiment will be described. As shown in FIG. 19, an
input unit 374 of an image forming apparatus 310 according to the
third exemplary embodiment is provided with a sheet-type input unit
74a, a sample output unit 74b for outputting a confirmation image
as a sample image to a sheet member P, and a selecting unit 374c.
The selecting unit 374c will be described later. Furthermore, as
shown in FIG. 18, the image forming apparatus 310 includes a
controller 336 that controls each component.
[0106] The following description relates to control of the
high-voltage power supply 68 by the controller 336.
[0107] The user sets a sheet member P in one of the containers 70
and touches the sample output unit 74b of the input unit 74 to
output a confirmation image. This causes the controller 336 to
revolve the transfer belt 50 and to control the toner-image forming
unit 30K and the first-transfer roller 52K, so as to transfer the
confirmation image onto the transfer belt 50 in step S2100 in FIG.
17. Furthermore, the controller 336 controls the high-voltage power
supply 68 so as to apply a voltage to the roller 32b. Moreover, the
controller 336 controls the transport device 18 so as to transport
the sheet member P contained in the container 70 along the
transport path 16.
[0108] In step S2200, the controller 336 causes multiple
confirmation images K02 with different voltage values of voltages
applied to the roller 32b to be formed on respective sheet members
P at the second-transfer section NT, as shown in FIG. 20. In
detail, the controller 336 controls the high-voltage power supply
68 to vary the voltage value of the voltage applied to the roller
32b, whereby multiple black-color confirmation images K02 are
formed on the respective sheet members P for the respective voltage
values. Accordingly, multiple black-color confirmation images K02
with different toner image densities are formed on the respective
sheet members P.
[0109] In this case, the controller 336 controls each component so
that, on each sheet member P, the value of a voltage applied to the
roller 32b when a confirmation image K02 is transferred onto the
sheet member P and the number of the confirmation image K02 are
formed. The value of the voltage and the number are an example of
information about the confirmation image K02.
[0110] In step S2300, the controller 336 acquires the number of a
confirmation image K02 input to the selecting unit 374c by the
user.
[0111] In detail, the user checks the confirmation image K02 on
each sheet member P output in step S2200. Moreover, the user
selects a confirmation image K02 with a toner image density closest
to a target toner image density and inputs the number of that
confirmation image K02 to the selecting unit 374c. Then, the
controller 336 acquires the number of the confirmation image K02
input to the selecting unit 374c by the user.
[0112] In step S2400, the controller 336 acquires the voltage value
of the voltage applied to the roller 32b when the selected
confirmation image K02 is transferred. Furthermore, the controller
336 acquires, from the ammeter 68a, the electric current value of
the electric current flowing when this voltage is applied to the
roller 32b. Then, the controller 236 calculates a print resistance
from the acquired electric current value and the acquired voltage
value.
[0113] In step S2500, the controller 336 determines whether or not
the acquired print resistance is lower than or equal to the system
resistance. If the print resistance is lower than or equal to the
system resistance, it is determined that the sheet member P is a
low-resistance medium, and the process proceeds to step S2600. If
the print resistance is higher than the system resistance, it is
determined that the sheet member P is plain paper, and the process
proceeds to step S2610.
[0114] In step S2600, if a toner image is to be transferred onto
the sheet member P determined as being a low-resistance medium, the
controller 336 controls the high-voltage power supply 68 to apply a
predetermined electric current to the roller 32b. Specifically, the
controller 336 performs constant current control to transfer the
toner image onto the sheet member P. Accordingly, the sequential
operation ends.
[0115] In contrast, when the process proceeds to step S3610 as a
result of the print resistance being higher than the system
resistance, the controller 336 applies a voltage of a predetermined
value to the roller 32b based on sheet-type information input to
the sheet-type input unit 74a by the user. The controller 336
performs constant voltage control in this manner to transfer the
toner image onto the sheet member P. Accordingly, the sequential
operation ends.
Conclusion
[0116] As described above, in the image forming apparatus 310,
multiple confirmation images K02 formed by varying the voltage
value are formed on respective sheet members P. Then, the
controller 336 acquires the number of a confirmation image K02
input to the selecting unit 374c by the user, and calculates a
print resistance from the voltage value and the electric current
value when that confirmation image K02 is transferred. Therefore,
the accuracy of a print resistance to be calculated may be
improved, so that the occurrence of a transfer defect of a toner
image onto a low-resistance medium may be suppressed, as compared
with a case where the print resistance is calculated without
varying the voltage value of the voltage applied to the roller
32b.
[0117] Furthermore, in the image forming apparatus 310, the voltage
value of the voltage applied to each confirmation image K02 and the
number of the confirmation image K02 are formed on the
corresponding sheet member P. Therefore, a confirmation image K02
may be readily selected by the user.
[0118] Furthermore, in the image forming apparatus 310, multiple
confirmation images K02 formed by varying the voltage value are
formed on respective sheet members P. Therefore, as compared with a
case where multiple confirmation images with different voltage
values are formed on a single sheet member P, the voltage value
does not have to be varied within a single sheet member P, so that
the toner image density of the confirmation image K02 transferred
onto the sheet member P is stable, whereby the accuracy of a print
resistance to be calculated may be improved.
[0119] Although specific exemplary embodiments of the present
disclosure have been described in detail, it is obvious to a
skilled person that the present disclosure is not limited to the
exemplary embodiments and that various exemplary embodiments are
possible within the scope of the disclosure. For example, although
not specifically described in the first exemplary embodiment, the
sample image may be or may not be transferred onto the sheet member
P in step S200, so long as the value of the electric current
flowing when the sheet member P is nipped at the second-transfer
section NT is acquirable.
[0120] As an alternative to the second or third exemplary
embodiment in which the electric current value for a low-resistance
medium preliminarily stored in the image forming apparatus 210 or
310 is used when constant current control is performed, an acquired
electric current value may be used in step S1400 or S2400.
Accordingly, even when an electric current value for a
low-resistance medium is not preliminarily stored, constant current
control is executed on a low-resistance medium.
[0121] As an alternative to the second exemplary embodiment in
which multiple detection images K01 are formed on a single sheet
member P, multiple detection images may be formed on respective
sheet members P. In this case, the advantage achieved by forming
multiple detection images K01 on a single sheet member P is not
exhibited.
[0122] As an alternative to the third exemplary embodiment in which
multiple confirmation images K02 formed by varying the voltage
value are formed on respective sheet members P, multiple
confirmation images K02 may be formed on a single sheet member P.
However, in this case, the advantage achieved by forming multiple
confirmation images K02 on respective sheet members P is not
exhibited.
[0123] As an alternative to the third exemplary embodiment in which
the voltage value of the voltage applied to the roller 32b is
displayed on each sheet member P, the voltage value does not have
to be displayed. However, in this case, the advantage achieved by
displaying the voltage value on the sheet member P is not
exhibited.
[0124] The foregoing description of the exemplary embodiments of
the present disclosure has been provided for the purposes of
illustration and description. It is not intended to be exhaustive
or to limit the disclosure to the precise forms disclosed.
Obviously, many modifications and variations will be apparent to
practitioners skilled in the art. The embodiments were chosen and
described in order to best explain the principles of the disclosure
and its practical applications, thereby enabling others skilled in
the art to understand the disclosure for various embodiments and
with the various modifications as are suited to the particular use
contemplated. It is intended that the scope of the disclosure be
defined by the following claims and their equivalents.
* * * * *